Seven-time Grand Slam champion Venus Williams brushed off talk of retirement on Monday despite flopping out of the Australian Open after a marathon clash with 22nd seed Ekaterina Makarova.

Seven-time Grand Slam champion Venus Williams brushed off talk of retirement on Monday despite flopping out of the Australian Open after a marathon clash with 22nd seed Ekaterina Makarova.

The former world number one was unseeded in Melbourne despite playing 11 events last year and making three semi-finals, and she looked on course for victory after winning the first set.

But a series of unforced errors and failure to convert crucial break points cost her dearly and she was sent packing by the Russian at the first hurdle 2-6, 6-4, 6-4 after a nearly two-and-half-hour epic in blazing hot conditions.

It was the 33-year-old American's worst performance at Melbourne Park since crashing in the first round in 2006, but she is determined to be back.

"I love Australia. I'd love to come back," she said, denying that a debilitating auto-immune disease and the constant travel was wearing her down.

"The last 12 months I have had issues, but this year I definitely am looking forward to having a good run and feeling well.

Williams hasn't won a Grand Slam since Wimbledon in 2008 and is without a title since Luxembourg in October 2012, but she made the final of the warm-up Auckland International, losing a three-set final to Ana Ivanovic.

It put her in good stead for Melbourne but after being diagnosed with energy-sapping Sjogren's Syndrome in 2011, and adopting a raw foods diet to ease her symptoms, she pulled out of last week's Hobart International to rest.

It appeared to pay dividends as a fresh Williams got an early break to go 2-0 up before the Russian immediately broke back.

Her trademark booming serve was firing and she was also returning well, sending some sizzling winners off her backhand to secure two more breaks and take the first set in 31 minutes.

Despite searing heat on Margaret Court Arena, Williams was looking set and should have gone 5-2 up in the second but she threw away two break points and then lost her serve to be 4-3 behind.

She fought back to win the decisive next game on her fifth break point to level at 4-4, only to lose her next serve and then the set on a series on unforced errors as the pressure mounted.

Williams took an extended off-court break between sets to regroup, returning to race to a 3-1 lead in the third before a wild backhand allowed the Russian back into the match.

Williams was broken again to go 3-5 down and there was no way back as Makarova served out the match to line up a second round clash with American Irina Falconi.

"Obviously losing any match is, you know, never any fun, especially in a major," said Williams.

"I think she played really well, and I think just my level was a little bit too up and down."